It is a common practice to prefabricate buildings for domiciles and other purposes in modular units utilizing a composite wall structure which has an insulation body therein and which comprises an impregnated wood frame or truss construction and planking on opposite sides thereof, the interior of this structure being filled with, for example, mineral wool which serves as a thermal insulating material.
In general, the rock wool or mineral fiber insulation is fitted into the wood frame in the form of a mat and serves as a thermal lagging.
In such wall constructions, efforts must be made to prevent slipping of the thermal lagging material downwardly by gravity when the wall construction is erected as a vertical wall.
Various suggestions have been made as to how this migration of the thermal insulation by gravity in prefabricated wall structures can be avoided.
One approach has been to fasten the heat insulation material in place by bars. Another approach has been to press the insulation material into the wood structure in a fashion which prevents migration.
The planking can be synthetic resin-bonded wood-particle board, plastic board or composites of other materials which generally are bonded to the synthetic resin-impregnated frame structure by adhesives and/or conventional fasteners such as screws or nails.
In all cases it is important to provide a vapor barrier or moisture barrier within the composite wall structure against the planking covering the side of the frame which is intended to be the interior wall of the structure.
Absent a vapor barrier of this type, generally when the external temperature is lower than the dew point within the interior, there is a possibility of moisture entering the composite structure or the air trapped in the composite structure condensing on the insulation material to the detriment of the insulation effect, promoting migration of the insulation material, and possibly causing rot or other damage within the construction.
Indeed, once such condensation occurs, it may lead to further penetration of the wall structure and hence further condensation to the point that the insertion may be rendered completely ineffective or the prefabricated wall panel will have to be replaced.
Wood panels of the type with which the invention is concerned, generally are used in wood houses and for high grade prefabricated modular structures, the panels being made in a factory environment to permit assembly on the building site or even shipment of completed modules to the building site.